Mold for articles having undercut portions

ABSTRACT

A partible mold has complementary body parts defining a principal portion of the mold cavity and at least one independently movable end part defining a cavity portion having undercuts relative to parting of the mold at the principal parting line. The end part is movable relative to the mold body in a direction generally parallel to the principal parting line, the parting line between the separately movable end part and the associated body part being transverse to the principal parting line. The end part is retractable from the complementary body part to clear the undercut portions of the article for parting of the body parts and ejection of the article. The end part and its actuating mechanism are carried on extension wings of the complementary body part for handling as a unit in an automatic molding machine. After ejection of the article, the end part is closed for clamping operation in association with the body of the mold.

United States Patent [19] Turner et a1.

[ Aug. 21, 1973 MOLD FOR ARTICLES HAVING UNDERCUT PORTIONS [73]Assignee: Continental Can Company, Inc.,

New York, NY.

[22] Filed: Dec. 22, 1969 [21] Appl. No.: 887,015

[52] US. Cl. 425/450, 425/326 B, 425/342,

425/DIG. 58 [51] Int. Cl. B29c 1/16 [58] Field of Search 18/34 R, 30 WM,30 WP,

18/42 R, 5 B, 30 LT, 5 BB, 16 T; 249/187, 161; 74/110; 425/326 B, 342,450, 451, 441,

Primary Examiner-H. A. Kilby, Jr. Att0rneyGeorge E. Szekely, Joseph E.Kerwin and William A. Dittmann {5 7] ABSTRACT A partible mold hascomplementary body parts defining a principal portion of the mold cavityand at least one independently movable end part defining a cavityportion having undercuts relative to parting of the mold at theprincipal parting line. The end part is movable relative to the moldbody in a direction generally parallel to the principal parting line,the parting line between the separately movable end part and theassociated body part being transverse to the principal parting line. Theend part is retractable from the complementary body part to clear theundercut portions of the article for parting of the body parts andejection of the article. The end part and its actuating mechanism arecarried on extension wings of the complementary body part for handlingas a unit in an automatic molding machine. After ejection of thearticle, the end part is closed for clamping operation in associationwith the body of the mold.

4 Claims, 12 Drawing Figures Patented Aug. 21, 1973 7 Sheets-Sheet lINVENTORS HOWARD M. TURNER DOMAS ADOMAlT/S ATT'Y.

Patented Aug. 21, 1973 3,753,641

7 Sheets-Sheet 2 INVENTORS HOWARD M. TURNER DOMAS ADOMAlT/S ELMER BQ/KPatented Aug. 21, 1973 7 Sheets-Sheet I5 /NVENTORS HOWARD M. {ya/ya?DOMAS ADGMA/K/S ELMER 4.50m BY M1 e 1 ATT Y Patented Aug. 21, 19733,753,641

7 Sheets-Sheet A IN VE N TORS HOWARD M. TURNER DOMAS ADOMAITIS EL MER J.2801K BY M Z Patented Aug. 21, 1973 7 Sheets-Sheet 3 llllllllllllllwINVENTORS HOWARD M. TURNER DOMAS ADOMAITIS;

ELMER J .5000.

) ATT'X BYM? Patented Aug. 21, 1973 3,753,641

7 Sheets-Sheet 6 INVENIORS HOWARD M Tumvm DOMAS ADOMAIT/S ELMER wFJI wfwPatented Aug. 21, 1973 7 Sheets-Sheet 7 INVENTOQS HOWARD M. TURNER DOMASADOMAIT/S ELMER {$801K BY A M W ATT'Y MOLD FOR ARTICLES HAVING UNDERCUTPORTIONS BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to mold assemblies, particularly of the types used inblow-molding machines, wherein molds are carried in series on a wheel,turret, conveyor or similar carrie.

2. The Prior Art Automatic blow molding machines are well known. In arepresentative machine a wheel carries a series of molds. Each mold isclosed on a parison at one station, the article is blown in passage andthe mold is then opened to eject the completed article at a succeedingstation. The molds are usually partible on a line in a plane of aprincipal axis of the article, such as a bottle. The bottle is ejectedfrom the mold in a direction transverse to the parting line. A typicalbottle so made has a concave bottom, which presents an undercut relativeto removal of the article from the mold.

Slight undercuts can usually be accommodated without tearing or otherdamage to the article in removal from a single split mold, because ofthe generally flexible condition of the article. However, if the bottledesign involves a relatively deep bottom concavity, or sidewallundercuts, such as in a series of flutes, the bottle cannot be readilyejected from a two-part mold, without damaging the article. Therefore,some provision must be made for clearing the undercut portion of thearticle before the mold can be fully opened to remove or eject thearticle. It has been proposed to provide a plug or cap for the mold toform the undercut bottom, which cap or plug can then be withdrawnaxially before opening the principal or body portion of the mold toremove the article. However, with this arrangement the plug or cap mustbe fully disengaged from the body parts of the mold, either or both ofwhich must be moved transversely to complete opening of the mold.Furthermore, the provisions for end part actuation, guidance and lock-upwith the plug or cap arrangement generally involves such increase in theoverall length of the mold assembly as to preclude close spacing ofmolds in an end to end series, as found desirable in such apparatus aswheel-type molding machines. In such machines the principal mold openingand closing movement is best effected radially of the wheel, with theprincipal axis of the mold tangential to the wheel for reception of theparison, which is part of a continuously extruded tube. Also, nosatisfactory arrangement has hitherto been devised for fullyself-contained actuation mechanism carriable with the mold as a compactintegral assembly and which will assure proper alignment and tightclosing of the mold parts in repeated opera tion.

SUMMARY OF THE INVENTION A principal object of this invention is toprovide a partible mold assembly so constructed as to facilitateejection from the mold of articles having undercut portions.

It is another object of this invention to provide a blow mold assemblyparticularly suitable for automatic production molding operations,wherein the mold is partible in two directions.

It is a further object of this invention to provide a blow moldstructure for the production of plastic bottles or the like, wherein atleast one bottom-end part of the mold is actuable for openingindependently of the opening of the body parts, whereby to provide forclearing bottom-end undercuts of the article prior to opening the bodyof the mold for removal of the article therefrom.

It is yet another object of the invention to provide in association witha blow mold including three or more parts separable from each otheralong principal and transverse parting lines, actuating mechanism,including power means, compactly arranged in association with the moldparts and carried therewith in a selfcontained assembly adaptable tomachines of the continuously-operating type.

A still further object of this invention is to provide for parison wasteseparation in the course of end-part actuation, obviating a separatetrim operation for such purpose.

The foregoing and other objects of this invention are achieved by meansof a mold assembly including body parts, or sections, partible along aprincipal parting line and one or more end parts partibly associatedwith the body parts, each matching end part and body part constituting amold section when matched to each other in closed condition. In oneembodiment, an end part is actuable for motion relative to theassociated body part along a line parallel to the principal partingline. In another form, end parts are slidable along diverging lines,separating from each other in a continuous motion simultaneously withopening relative to the body of the mold. The slide paths areestablished as required for clearing undercut portions of the articleformed by the end parts of the mold.

In preferred forms of the invention, end part actuation is provided byfluid power cylinders and toggle mechanism, arranged to lock the moldparts in closed position. The cylinders and associated toggle mechanismare retained by the respective body mold parts, facilitating adjustmentfor tight closing, smooth actuation and accurate positioning of theseveral parts during repeated operations, with minimum attention forreadjustment or other maintenance. Pivotal mounting of the powercylinder provides accommodation for linkage motion, obviating binding,and dispensing with unduly complex linkage.

It is not necessary in all cases that both end parts be movableindependently of the body parts. Some articles cannot safely be pulledfree of a fixed, solid section, but can be knocked out of the movablesection carrying it, with a flexing or tipping action. In such case, theend part associated with the fixed section is partible and actuable asabove described, but the end part associated with the movable bodysection may be integral therewith. Just prior to opening actuation ofthe movable mold section, the independently movable end part is partedfrom the fixed body part, thus clearing the undercut in the fixedsection, permitting ready withdrawal of the article with the movablesection, whereupon the bottle can be readily ejected.

Another feature of blow-mold structure according to this invention isautomatic, clean cutoff of the bottom waste or parison tail. When theparison is pinched closed as the mold is closed, a thin film of wasteoften remains between the pinch edges of the end parts. Upon moving theend parts, or one of them, away from the body of the mold, the waste iscleanly severed by tearing or shearing adjacent the weld line, leaving asmooth weld line, with virtually no flash, so that subsequent trimmingor buffing is not required.

Other features and advantages will be apparent from the followingdescription and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial elevation of ablow mold wheel in outline, showing some of a series of molds or moldassemblies according to this invention at their opening stages;

FIG. 2 is a partial longitudinal section through one of the moldassemblies of FIG. 1, the section being taken at right angles to theprincipal parting line of the mold when closed, showing details of themold assembly;

FIG. 3 is a partial transverse section on line 3-3 of FIG. 2, showingthe undercut condition relative to the principal mold parting line;

FIG. 4 is an end view of the closed mold assembly as shown in FIG. 2;

FIG. 5 is a partial section similar to FIG. 2, but showing the end partsand actuating mechanism in the open position of the end parts;

FIG. 6 is a section similar to that of FIG. 2, showing a modified formof actuating mechanism, with. the end parts retracted;

FIG. 7 is a section similar to FIG. 6, but showing the parts in closedposition;

FIG. 8 is a partial section similar to FIG. 2, showing another form ofthe invention;

FIG. 9 is a partial section similar to FIGS. 2 and 8, showing yetanother form of the invention;

FIGS. 10 and 11 are enlarged partial sections of the end parts of theassembly shown in FIG. 2, illustrating the waste severance action of theparts upon retraction; and

FIG. 12 is a schematic partial view of a mold wheel as shown in FIG. 1,illustrating a molding cycle and showing the arrangement and operationof control apparatus in association with the molds according to thisinvention.

DESCRIPTION OF PREFERRED EMBODIMENT For purposes of illustration, theinvention will here be described in association with a production blowmolding machine of the vertical rotary or wheel type, the generalconstruction and operation of which is shown and described in commonlyassigned US. Pat. No. 2,784,452 issued Mar. I2, 1957 to Herbert S.Ruekberg and John L. Szajna.

FIG. 1 shows a portion of a mold wheel such as that shown in theaforesaid Ruekberg and Szajna patent, including three molds or moldassemblies 10-11 12-13 and 14-15, constituting part of a series of moldscarried on a plurality of arms 16 attached to hub 17 for continuousrotation in the clockwise direction as here shown and as indicated bythe direction arrow. The various molding operations are performed duringrotation of the hub or wheel 17, a complete cycle for one mold takingplace during each revolution.

The successive arms 16 shown in FIG. 1 are in passage through themold-opening stages of the cycle, mold 10-11 being closed and carryingthe blown article, here shown as a bottle 18. Mold 12-13 is partiallyopen and mold 14-15 is fully open, preparatory to knockout of thecompleted bottle 18 arried in outer mold half 14, the outer half of themold being in this arrangement radially movable under control of the camtrack 19. The molds are successively closed to the condition of mold10-11 in another stage during the revolution of the mold wheel, undercontrol of a closing cam track segment, not here shown.

In the foregoing general description of the machine the terms openingand closing" have been employed in reference to a principal parting lineindicated at 20 between mold halves 10-11 such being the opening andclosing action required for production of articles of types heretoforeconsidered suitable for molding in the type of machine described.

According to this invention, mold structure and associated actuationmechanism are provided in forms particularly adaptable to machines ofthe type above generally described, with the same general operation, tofacilitate production of articles in types or shapes not heretoforeconsidered practicable for production in such machines, notably articlesinvolving undercuts precluding satisfactory ejection of the article frommolds heretofore known. Representative of such articles are bottleshaving deep bottom concavities, a series of axial bottom-end flutes, orthe like.

FIG. 2 illustrates the construction of a mold assembly according to thisinvention, as adapted for use in the machine of FIG. 1. Mold sections 10and 1 1 include respective mold body parts 21 and 22, defining theprincipal or body-forming cavity 23. Body parts 21 and 22 are partiblewith sections 10 and 11 along parting line 20 which general or principalparting line is in a plane including the axis of the cavity 23.

The bottom-end forming portion of the mold 10-11 consists ofcomplementary mold end parts 24, 25, mating with each other along theprincipal parting line 20 and with respectively associated body parts 21and 22 along the transverse parting line 26.

The cavity walls of end parts 24 and 25 are contoured to form a concavebottom end and generally lengthwise flutes on the bottle to be molded,as provided for by the corresponding bottom wall 27 and the several ribs28 around the end cavity 29. The wall 27 and certain ones of ribs 28constitute undercuts relative to parting along the principal partingline 20, the condition as to the rib portions 28 nearest line 20 beingbest seen in FIG. 3, wherein the bottle 18 is indicated in broken lines.

Referring again to FIG. 2, the end parts 24 and 25 are provided withopposed lands or edges 30, 31, which serve to pinch and weld the parisonand so to hold the parison sealed during blowing, with the mold fullyclosed, its condition in FIG. 2.

In order to assure accurate alignment in closing the mold upon repeatedactuations of the end parts 24 and 25, the same are carried and guidedupon portions of the respective mold halves or sections 10 and 11,carrying body parts 21 and 22. Compactness and simplicity are providedby encasing the end part actuation means, assembly or, mechanism,comprising linkage and motive power means or units, in the mold halves10 and 11, as seen in FIG. 2. The construction and operation of the endpart actuation mechanism and arrangement for support and guidance arebest understood by reference to FIGS. 2 to 5 inclusive, FIGS. 2 to 4showing the position of the parts with the mold fully closed, and FIG. 5showing the position of the parts with the end parts 24 and 25 fullyretracted, but the body parts 21 and 22 in their closed positions.Inasmuch as the construction and arrangement for both end parts areidentical, the description hereafter will refer in detail only to endpart 24, carried by the outer mold half 10.

The direction of end-part opening motion is established according to theparticular end configuration of the article. In the case hereillustrated, linear motion of the end part 24 away from the body part 21at a small angle to the principal parting line provides draw suitablefor freeing the end part 24 from the article or bottle 18. Therefore,the end part 24 is guided on opposite sides by paralle, angularlyextending rails 34 and 35 formed respectively on the retaining plates orretainers 37 and 38 affixed to wings 40 and 41, which extend endwisefrom mold half 10.

Edges 43 and 44 of respective inserts 46 and 47 and correspondinglyopposed rail edges 34 and 35 define guideways 49 and 50 to receive theguide flanges 52 and 53, which extend laterally from end part 24 and fitclosely in the guideways. The body of end part 24 is a close sliding fitbetween guide faces 55 and 56 of retainers 37 and 38, maintaininglateral alignment of end part 24, while guideways 49 and 50 maintain thevertical alignment. Thus, end part 24 is precisely held to a prescribedpath of movement to and from its closed position in true alignment withits associated body part 21. Coolant circulation pipes 54, connected toend parts 24 and 25, glide back and forth in slots 57 as the end parts24, 25 are actuated in retracting and closing movements.

The actuation apparatus or mechanism associated with end part 24comprises the double acting cylinder 58, clevis 59 and link 60. Thispower toggle mechanism serves to drive end part 24 on its prescribedpath between its closed and retracted positions and to clamp part 24 inits closed position. Cylinder 58 is housed in chamber 62 of mold half 10with head end 63 pivotally supported on shaft 64, which is trunnioned inmold half 10. Piston rod 66 is affixed to clevis 59 which is pivotallyconnected to link by means of pin 67. Link 60 pivots about pin 68 whichis trunnioned in opposed angle clips 69 and 70. Clips 69 and 70 areclamped between blocks 72 and 73 and pads 74 and 75 respectively. Link60 extends into the pocket 77, the end of the link being trunnioned onpin 78.

Referring now particularly to FIG. 2, the admission of pressure fluidinto cylinder 58 on the head side of piston 79 clamps end part 24against body part 21, the corresponding actuation of the duplicatemechanism associated with end part 25 effecting and maintaining tightclosure between end part 25 and body part 22.

In its application to blow molding, the end part actuating mechanismsabove described are actuated while the mold halves l0 and 11 areseparated preparatory to parison capture. Thus, the mold assembly formedof the four parts 21, 22, 24 and 25 operates to capture the parison asthough the mold were a two-part mold consisting of halves l0 and 11. Thereaction to parison clamping pressure and component of blow pressure onthe end parts, transverse to the parting line 20, are taken on the links60 substantially as pure columnar load, the links being held in suchcolumnar position by pressure in the cylinders 58, which pressure ismaintained at a value sufficient to overcome the blow pressure loadcomponent parallel to line 20 tending to move parts 24 and 25 in thedirection away from corresponding body parts 21 and 22. This endwiseload is taken substantially axially of the rods 66. That is, link 60 androd 66 constitute a substantially rectilinear toggle, minimizing bendingstresses in the parts, rods and links, distortion of the links beingsubstantially obviated by virtue of alignment of the respective endparts axially of the links. The pivots are spaced to effect mechanicaladvantage in favor of the closing pressure exerted by the cylinders 58,so that the necessary holding force can be developed with relativelysmall cylinder diameter and moderate fluid pressure, the mold assemblythus being quite compact.

When the bottle has been fully blown and suitably cooled, pressure isadmitted to cylinders 58 on the rod side of the piston 75, while thehead sides are exhausted, effecting retraction of the end parts 24 and25, along the lines determined by the guideways above described, to theposition of FIG. 5, freeing the end of the bottle for separation of themold halves 10 and 11. A self-alignment characteristic is provided byslots 81 at the engagement of links 60 with the driven pins 78 and bysupporting the cylinders 58 on trunnions 64. These provisions permit theuse of a simple crank action in lieu of more complex, bulkier andcostlier mechanism. Also, by positioning of pin 78 to effect reactionforce, near the center of gravity of the end part 24, warpage of the endpart 24 is substantially obviated.

Suitable actuation control is described subsequently.

MODIFICATIONS The form of the invention above described is particularlysuitable for mass production blow molding of bottles or similar articlesof various sizes on a machine such as that shown in FIG. 1. However, itwill be understood that the invention is not limited to the particularform or adaptation, or to blow molding, but can be adapted to otherapplications, other machines, or for semi-automatic or manuallycontrolled operation. Variations and modifications can be readily made,to suit various conditions or requirements.

Pneumatic actuation and clamping by means of the cylinders 58, abovedescribed, provides desirably fast action. However, hydraulic rams,motors, solenoids or the like can be readily substituted, if preferred.

Where particularly high clamping and holding pressures are involved, aself-locking toggle is preferred, for maximum assurance against rock orcreep and consequent loss or inequality of clamping pressure. Suchtoggle mechanism is shown in FIGS. 6 and 7, wherein parts correspondingto those previously described are given like reference numberals withthe addition of 100. FIG. 6 shows the condition of the linkage in theretracted position of end part 124, while FIG. 7 shows the linkagecondition corresponding to closed position of the end part.

Rod 166 of cylinder 158 carries block 159, with pivot pin 167 drivingthe double-crank links 180 around the anchored pivot pin 183. Links 180are pinned to drive link 186, which actuates the toggle link 187 aboutanchored pin 168. The other toggle link 188 carries part 124 by means ofpivot pin 178. Head-side actuation of the cylinder 158 throws thelinkage to the position of FIG. 7, clamping and locking part 124 to bodypart 121, part 124 being configured and guided substantially asdescribed in association with the form of FIGS. 2 to 5. By virtue ofclamping edge being inward of pivot pin 178, clamping pressure andresultant torque are effective in a direction to maintain toggle links'187 and 188 in locked position shown. Lateral component of blowpressure in cavity 129 acts similarly, while end thrust is borne by thecolumn formed by links 187 and 188, hinging on pin 168. Also, thegeometry of the linkage is such as to require only a very short strokeof rod 166, whereby cylinder 158 may be comparably short, thusconserving in length of the mold assembly required for housing theactuating mechanism. This space conservation is particularly desirablefor molds carried on a wheel, providing maximum production for givenwheel size and speed.

In cases where space permits, direct actuation of the end parts can beprovided as shown in FIG. 8, wherein parts corresponding to those ofFIGS. 2 to 5 are correspondingly numbered with the addition of 200. Inthis form the actuation cylinders 258 are anchored in chambers 240 and241 of mold halves 210 and 21] respectively, the cylinders being alignedwith the respective end parts 224 and 225, which are configured andguided substantially as shown for the corresponding end parts in FIGS. 2to 5. Piston rods 266 are connected directly to the respective end parts224,225. As observed previously, the angle of inclination for the pathsof the end parts relative to the principal parting line 220 is dictatedby the cavity configuration, with respect to clearing the article uponretraction of the end parts. The conditions in this respect are shownthe same in FIG. 8 as in FIGS. 2 to 5.

In some cases it is not necessary that both end parts be retractable.Such a case is illustrated in FIG. 9, wherein parts corresponding tothose shown in FIGS. 2 and 5 are given like reference numerals with theaddition of 300. In the modification here shown the end parts 324 and325 are configured for forming a concave bottom on a bottle, but thereare no other details presenting problems of withdrawal or ejection ofthe article from the mold.

The arrangement shown in FIG. 9 is one designed for use in the machineshown in FIG. 1, wherefor upper or outer mold half 310 is laterallymovable to open the mold, while lower or inner half 311 is fixedrelative to its support. Accordingly, end part 325 is retractablerelative to the associated inner mold half 311, while end part 324 isfixed to mold half 310. End part 324 may be formed as part of mold half310, if desired, but is preferably a separate piece machinable with endpart 325, for economical manufacture with precision finishing. End part325 is arranged for sliding in wing extension 341 of mold half 311,substantially in the manner shown for the corresponding parts in formspreviously described. However, in this case the article can be clearedfor withdrawal from mold half 311 by retracting end part 325 on a lineparallel to principal parting line 320, the drawing showing part 325 inretracted position. Retraction and closure are effected by means of thecylinder 358, which is provided with a trunnion 364 for pivotal supporton a pair of brackets 391, of which one is here shown, the bracketsbeing affixed to wing 341. Clevis 359 on piston rod 366 is pivotallyconnected to toggle linkage 360 by means of pivot pin 367. Link 387 ispivotally supported on wing 341 by pin 368, while link 388 is pivotallyconnected to end part 325 at pin 378. Links 387 and 388 form a lockingtoggle, similar to that of FIGS. 6 and 7, effective to clamp end part325 to body part 311 when rod 366 is actuated in its outward stroke,cylinder 358 assuming the position shown in broken lines when end part325 is in its closed position.

After an article is molded, and end part 325 is retracted to the openposition shown, the article 318, captive in movable half 310, is drawntherewith from mold half 311, whereafter the article can be ejected frommold half 310 by rapping the article at its end remote from end part324, causing the article to tip clear and fall out of the half-moldcavity, as shown in the broken lines.

WASTE SEVERANCE The several forms of the invention above described areadapted for blow molding apparatus, wherein the tubular parison ispinched closed adjacent the mold cavity. The pinched condition as itprevails in use of the mold assembly of FIG. 2 is illustrated in FIG.10. The drawing shows the position of the parts and the condition of theparison with the mold closed and the parison fully blown to form thearticle 18, of which the bottom end is shown adjacent the pinch-off. Theconstruction and operation of the mold parts is such that the wasteportion of the parison is automatically and cleanly severed from thearticle upon retraction of the end parts 24 and 25, as seen in FIG. 11,even should the pinch-off lands fail to effect full severance uponpinch-off.

In FIG. 10, the parison is shown pinched and welded under clampingpressure with a film of parison material between the pinch-off edges 30and 31, which taper to effect minimum clearance therebetween at cavitybottom wall 27. The waste portion of the parison is captured between theopposed end part surfaces 93 and 94, forming shoulders 95 and 96 on theparison waste. Upon retraction of the end parts 24 and 25, these partsmove toward the position of FIG. 5, the position of FIG. 11 beingintermediate. Parts 24 and 25 bear on the shoulders 95 and 96,tensioning the thin web of the waste from the article 18, the materialbeing thinnest at the line of attachment by virtue of the tapered edgelands above noted. It has been found in practice that this severance issufficiently clean and flush as generally to obviate residual flash onthe article 18, thus dispensing with a separate flash trimming orbuffing oper' ation along the weld line.

Similar waste cutoff occurs upon retraction of the end parts in the formof FIG. 6 and of the lower end part 325 in the fonn of FIG. 9. In thelatter case, in addition to the tensile force on the waste film there isa shearing action between the pinch-off lands 330 and 331 consequentupon the endwise movement of part 325 relative to end part 324.

AUTOMATIC CONTROL The mold assembly of this invention is readilyadaptable to automatic control. In the rotary molding machine shown inFIG. 1, each mold passes through several stages, comprising clamping,blowing, cooling, opening, article ejection and closing. At clamping,blowing and cooling stages, the mold is fully closed. After the articleis sufficiently cooled to be selfsustaining, the mold is opened, and thearticle ejected, whereafter the molding cycle is repeated.

Control of mold actuation in the machine of FIG. I, with the moldassembly of FIG. 2, is shown schematically in FIG. 12. In the latterview the mold assembly rotates clockwise, as in FIG. 1. Radial movementof outer mold half 10, for opening and closing with respect to half 11,is controlled by followers 97 and 98 riding corresponding segments oftrack 19. Closing and retraction motions of end parts 24 and 25,relative to corresponding halves l and 11 respectively, are controlledby the condition of two-position valve 99 serving cylinders 58, inresponse to actuation oflimit switch 100.

At station A the mold is fully closed, with parts 10, ll, 24 and 25clamped together and on the parison. This mold condition obtains as themold proceeds around the track to stage B, parts 24 and 25 being clampedto parts 10 and 11 by virtue of pressure on the rod side of cylinders58, admitted through valve 99, while the cylinder head ends areconnected to exhaust. Parts 10 and 11 are held closed by cam segment 119acting on follower 98. At station C a cam 101 actuates limit switch 100to reverse the position of valve 99, admitting air into the head ends ofcylinders 58 and exhausting the rod ends, thus effecting retraction ofendparts 24 and 25. Thereafter, the opening control follower 97 entersthe opening track segment 219, drawing mold half 10 open, as shown instation D, reaching full open position prevailing at station E, endhalves 24 and 25 remaining in the retracted position. The article isejected while the mold is fully open. At station F cam 102 trips limitswitch 100, repositioning valve 99 to restore end parts 24 and 25 totheir closed positions, preparatory to closing and clamping of halves 10and 11, as follower 98 travels cam segment 319 in progress at station Gand completed at station A, from which the cycle repeats.

Thus, the closing and opening action of end parts 24 and 25independently of closing and opening of halves l0 and 11 facilitatescorrespondingly independent timing, whereby to assure that undercutinterference is fully cleared before final parting of the mold and thatthe end parts are repositioned for clamping action be fore the clampingstage. With limit switch control and air cylinder actuation of the endpart motions, actuation is virtually instantaneous, so that there is nosacrifree of cycle time from the other operations, which proceed as inthe production of similar articles not involving the undercut problem.Accordingly, the mold apparatus and control according to this inventioncan be incorporated in a standard machine interchangeably with othermolds, without basic cycle modification or major structural changes inthe machine and its auxiliaries. In the case of the blow molding machinedescribed, pressure air for the cylinders can be tapped from the linesproviding blow air to each mold, as regularly provided in suchapparatus, so that no special air manifold or other special supply isinvolved.

We claim:

1. A mold section for a partible mold including first and secondrelatively movable mold portions defining respective undercut bottomwall portion forming and body wall portion forming cavities, saidcavities defining coincident cavity surfaces in the closed position ofsaid mold portions, means for applying relative motion to said first andsecond relatively movable mold portions to move the cavity definingsurfaces thereof away from each other to an open position, said applyingmeans includes pivot means and toggle linkage means, said toggle linkagemeans being disposed between said pivot means and said bottom wallportion forming cavity, said pivot means includes a first stationarypivot pin, a link mounted upon said first stationary pivot pin, meansfor imparting motion to said link, said toggle linkage means includes atleast two links, one of said two links being pivotally secured to saidbottom wall portion forming cavity by a first pivot pin movabletherewith, and the other of said two links being pivotally secured to asecond stationary pivot pin.

2. The mold section as defined in claim 1 including another linkpivotally mounted between said first mentioned link and said two linksby respective movable pivot pins.

3. The mold section as defined in claim 2 wherein said first-mentionedlink is a bellcrank lever joined by a fourth movable pivot pin to saidrelative motion applying means.

4. The mold section as defined in claim 3 wherein said relative motionapplying means is a piston-cylinder fluid motor.

1. A mold section for a partible mold including first and secondrelatively movable mold portions defining respective undercut bottomwall portion forming and body wall portion forming cavities, saidcavities defining coincident cavity surfaces in the closed position ofsaid mold portions, means for applying relative motion to said first andsecond relatively movable mold portions to move the cavity definingsurfaces thereof awAy from each other to an open position, said applyingmeans includes pivot means and toggle linkage means, said toggle linkagemeans being disposed between said pivot means and said bottom wallportion forming cavity, said pivot means includes a first stationarypivot pin, a link mounted upon said first stationary pivot pin, meansfor imparting motion to said link, said toggle linkage means includes atleast two links, one of said two links being pivotally secured to saidbottom wall portion forming cavity by a first pivot pin movabletherewith, and the other of said two links being pivotally secured to asecond stationary pivot pin.
 2. The mold section as defined in claim 1including another link pivotally mounted between said first mentionedlink and said two links by respective movable pivot pins.
 3. The moldsection as defined in claim 2 wherein said first-mentioned link is abellcrank lever joined by a fourth movable pivot pin to said relativemotion applying means.
 4. The mold section as defined in claim 3 whereinsaid relative motion applying means is a piston-cylinder fluid motor.